1. Field of the Invention
This invention relates to an electronic endoscope system.
2. Description of Related Art
Typically, as schematically shown in FIG. 2, an electronic endoscope system comprises an electronic endoscope 101 which is inserted into a human body, a processing unit 102 and a monitor television (not shown). Such an electronic endoscope 101 has an objective lens 104 disposed at a distal end thereof, a solid state image pickup element 105 disposed in a focal position of the objective lens 104 and a light guide 103 which guides light from light source outside the electronic endoscope from one end to another end thereof and directs the light toward the inside of an organ of a human body. The processing unit 102 includes therein an illumination device comprising an illumination lamp 108 and energizing means 109 for the illumination lamp 108, an iris 107 operative to limit the diameter of the bundle of light rays, i.e. the quantity of light, emanating from the illumination lamp 108 or shut off the bundle of light rays emanating from the illumination lamp 108, and a focusing lens 106 operative to focus the light rays passing through the iris 107 at an end of the light guide 103. The light rays emanating from the illumination lamp 108 and focused on the end surface of the light guide 103 are transmitted by the light guide 103 and directed toward an object to illuminate it. Light rays reflected by the object are focused on the solid state image pickup element 105 by the objective lens 106 so as to form an optical image of the object on the solid state image pickup element 105.
The processing unit 102 includes a drive signal generating circuit 112, a black balance adjusting circuit 113, a white balance adjusting circuit 114, a video signal processing circuit 115 and a display control circuit 116 therein. Specifically, the drive signal generating circuit 112 generates a drive signal with which the solid state image pickup element 105 is driven and controlled to photo-electrically convert the optical image thereon into image signals. The image signals provided by the solid state image pickup element 105 are adjusted in black and white balances by the black balance adjusting circuit 113 and the white balance adjusting circuit 114, respectively. The adjusted image signals are subsequently processed for gamma correction etc. by the video signal processing circuit 115 and then converted to television signals Sv through the display control circuit 116 and transmitted to the monitor television to display an image of the object on the screen.
When a black balance adjusting command 18 is entered, an iris drive circuit 110 drives the iris 107 to close. While the iris 107 remains closed, the black balance adjusting circuit 113 is actuated to perform black balance adjustment for a specified period of time. Similarly, when a white balance adjusting command is entered, the iris drive circuit 110 drives the iris 107 to close. While the iris 107 remains closed, the white balance adjusting circuit 114 is actuated to perform black balance adjustment for a specified period of time.
In the electronic endoscope system, it is necessary to isolate the distal end portion, more specifically at least the solid state image pickup element, of the electronic endoscope from ambient light while completely closing the iris so as to prevent illumination light emanating from the lamp from reaching the light guide during performing black balance adjustment of the electronic endoscope 101, which is always troublesome adjustment operation.
It is therefore an object of the invention to provide an electronic endoscope system which has no necessity of closing an iris so as to shut off illumination light from an endoscope nor necessity of isolating an solid state image pickup element from ambient light during performing black balance adjustment.
The foregoing object of the present invention is accomplished by an electronic endoscope system comprising an electronic endoscope unit equipped with a photoelectric conversion element as an image pickup element for photo-electrically converting light from an object to electric signals and a signal processing unit for processing the electric signals to video signals, the processing unit comprising drive signal generating means for generating vertical and horizontal transfer signals as drive signals with which the photoelectric conversion element is driven, color balance adjusting means for adjusting at least black balance of the photoelectric conversion element, and transfer signal interruption means for interrupting the vertical transfer signals from the photoelectric conversion element and admitting the horizontal transfer signals to the solid state image pickup element so as to cause the photoelectric conversion element to perform horizontal transfer only while the balance adjusting means is actuated.